Apparatus for heating or cooling a meltable material

ABSTRACT

An apparatus for heating or cooling a meltable material in a container, comprising a heating element ( 10 ) and a holding device ( 20 ), the heating element ( 10 ) being of a tubular design, with an inflow opening ( 11 ) and an outflow opening ( 12 ) for a heat transfer medium to flow through, and being fastened to the holding device ( 20 ) movably in at least one spatial direction as the main direction of movement, wherein the apparatus also has a stirrer ( 30 ) for mixing liquid material through, which is likewise arranged movably in the main direction of movement.

The invention relates to an apparatus for heating or cooling a meltable material in a container, comprising a heating element and a holding device, the heating element being of a tubular design, with an inflow opening and an outflow opening for a heat transfer medium to flow through, and being fastened to the holding device movably in at least one spatial direction as the main direction of movement. The invention also relates to a method for melting a meltable material and to a method for cooling a molten material in a container that has an opening on its upper side, by means of an apparatus according to the invention.

A number of starting materials for the chemical or other processing industries, for example waxes, wax-like oligomers and polymers, fats, emulsifiers or salts, are in a solid or highly viscous state at ambient temperature (20° C. to 25° C.) and must be liquefied before they undergo further processing. The provision of considerable amounts of such materials involves a certain degree of expenditure. Such materials are usually transported and delivered in transporting containers such as drums or, for example, “Intermediate Bulk Containers” (IBC), which, depending on the type, generally have a capacity of 500 to 1000 liters. The containers have a filling opening of about 15 cm in diameter on their upper side and a drainage tap underneath.

Since the starting materials often constitute a mixture, it is generally required to melt and homogenize the complete content of a transporting container before a homogeneous partial amount can be removed from the transporting container and passed on for further processing, since it can be assumed that, during the preceding solidification process, the components have crystallized out at varying rates, and therefore the mixture in the container is not in a homogeneously distributed form.

The liquefying of the content of a transporting container is often carried out in what are known as heating cabinets, the container being placed in a closed, heated space in which it is heated as a whole by the air surrounding it. In the case of a further established method for melting the content of the container, the container is immersed in a tank with hot water and left there until the content of the container has melted. Both the heating cabinet and the immersion tank involve complicated structural measures and a high energy consumption. Also known are electrically operated heating bands and heating jackets, which are placed around the outer wall of the transporting container and transfer heat to the container wall. They are also not very energy-efficient.

A further disadvantage of the aforementioned methods can be seen in the fact that the heat transfer takes place indirectly via the container wall. Generally used as the material for the walls of IBCs is, for example, polyethylene (HDPE), which has a low thermal conductivity and a thermal resistance of approximately 100° C. Consequently, there are limits to the heating-up process with regard to the maximum admissible temperature, in order to avoid damage or even destruction of the container wall. Furthermore, with wall heating, the layers of the solid material that are near the wall melt first, so that in the course of the melting process layers of gas form between the solid material and the inner wall of the container, reducing the thermal conductivity still further.

Specifically for drums as transporting containers, there are known apparatuses in which heating does not take place indirectly via the drum wall, but in direct contact with the material to be melted. In laid-open patent specification DE 37 06 927 A1 there is a description of a drum melting apparatus which comprises a horizontally arranged tube spiral through which hot steam is made to flow. The tube spiral is placed onto the material to be melted and, as the melting process proceeds, slides down in a mounting in the drum under the influence of gravitational force.

The document RU 2 159 671 C1 discloses a similar apparatus, which is likewise intended for liquefying solid, meltable contents of drums. Also in the case of this apparatus, a horizontally arranged tube spiral is placed onto the material to be melted and slides down in the drum as the melting process proceeds. The tube spiral is flowed through by a liquid heating medium, the temperature of which can be set.

While the two aforementioned apparatuses are suitable for liquefying the content of drums, they are only suitable to a limited extent for melting material in a container such as an IBC. This is so because, by contrast with drums, in which the cross section of the opening is of the same order of magnitude as the cross section of the drum, the openings of containers are usually much smaller than the cross section of the container. Although it is possible with the known apparatuses to melt vertical channels into the material in a container, it takes a very long time before the entire material is liquefied, if it is possible at all.

The object is to provide an apparatus with which solid or highly viscous materials in transporting containers can be liquefied homogeneously and energy-efficiently in a short time.

This object is achieved according to the invention by an apparatus for heating a meltable material in a container, comprising a heating element and a holding device, the heating element being of a tubular design, with an inflow opening and an outflow opening for a heat transfer medium to flow through, and being fastened to the holding device movably in at least one spatial direction as the main direction of movement, the apparatus also having a stirrer for mixing liquid material through, which is likewise arranged movably in the main direction of movement. As described further below, the apparatus according to the invention can also be used for cooling a meltable material in a container.

The apparatus may also be designed to be movable in two or all three spatial directions. The main direction of movement is understood as meaning the direction in which the heating element and the stirrer can be moved into the container and out of the container. In a preferred embodiment, the holding device is designed in such a way that the heating element and the stirrer are movable in the vertical direction as the main direction of movement through an opening in the upper side of the container.

The heating element according to the invention is tubular and can be flowed through by a fluid heat transfer medium. The cross section of the tube may have different forms; it is preferably circular, oval or rectangular, in particular circular. The heating element is preferably produced from a material which has a high heat transfer coefficient. It is particularly preferred for the heating element to be produced from high-grade steel, aluminum or copper. The wall thickness is preferably from 1 to 2 mm, the inside diameter from 0.5 to 3 cm.

In the case of a particularly advantageous embodiment, the heating element comprises a tube helix, which has a hollow-cylindrical contour. This configuration offers a large heat transfer area in a limited space. It is also preferred that the cylinder axis corresponds substantially to the main direction of movement. This has the advantage that, with a given cross section of the container opening, the outside diameter of the tube helix can be chosen to be as large as possible, without the opening being skewed when the heating element is moved in and out. A deviation of up to 10° between the hollow cylinder axis and the main direction of movement is considered to be still tolerable.

In order to ensure a liquid flow through the hollow cylinder not only in the axial direction but also in the radial direction, a distance between the tube portions of the helix in the axial direction is preferably provided. The axial distance between neighboring tube portions is preferably from 20% to 400%, particularly preferably from 50% to 200%, of the outside diameter of the tube.

In the case of a preferred configuration, the tube helix comprises two part-helixes with the same outside diameters of the hollow cylinders, the part-helixes running one into the other in the axial direction, being connected to one another at their respective one end and opening out into the inflow opening or the outflow opening with their respective other end. Also in the case of this embodiment, axially neighboring tube portions are preferably kept at a distance. In a further preferred variant, the part-helixes are arranged in such a way that the axial distance between neighboring tube portions is alternately 0% and from 50% to 400%, particularly preferably from 100% to 300%, of the outside diameter of the tube. This means that on one axial area the part-helixes are touching, while the other areas are at an axial distance in the range specified.

In the case of a further preferred configuration, the tube helix comprises two part-helixes with different outside diameters of the hollow cylinders, the part-helixes running one into the other in the radial direction, being connected to one another at their respective one end and opening out into the inflow opening or the outflow opening with their respective other end.

Both configurational variants are also referred to hereafter as double helixes. The inflow opening and the outflow opening are preferably located on the end face of the hollow cylinder that is facing away from the container during moving in and out.

The heating element is preferably dimensioned in such a way that the ratio of its length to its outside diameter is from 1 to 10, particularly preferably from 1.5 to 8, in particular from 2 to 6. The outside diameter of the heating element is preferably from 4 to 60 cm, particularly preferably from 8 to 20 cm, in particular from 10 to 16 cm. A length of 60 cm to 120 cm has proven to be advantageous for a number of applications.

In a preferred embodiment of the apparatus according to the invention, the stirrer comprises a stirrer shaft, on which at least one stirring element is arranged, and the axis of which corresponds substantially to the main direction of movement. In the case of embodiments with a hollow-cylindrical heating element, the stirrer shaft is preferably arranged inside the hollow-cylindrical tube helix, particularly preferably coaxially in relation to the cylinder axis.

The stirrer shaft may be driven by known motors and gear mechanisms, for example electrically or pneumatically. The axial and vertical flow conditions in and around the heating element can be set by the choice of stirring elements. Appropriate stirring elements, for example blade, disk, cross-arm, impeller, anchor or propeller stirrers, are known to a person skilled in the art. The stirring elements are preferably made from high-grade steel; depending on the application, enamelled or, for example, Teflon-coated stirring elements have also proven to be successful in counteracting product attachment. The stirring elements are preferably fastened to the stirrer shaft adjustably and/or exchangeably.

In a preferred embodiment, the stirrer is arranged in such a way that it can be moved together with the heating element in the main direction of movement. In this case, for example, components in which the stirrer is mounted may be fixedly connected to the heating element or the holding device.

In a further preferred embodiment, the heating element and the stirrer are arranged movably in the main direction of movement independently of one another. In this case, components in which the stirrer is mounted may be connected to the heating element in such a way that the stirrer is movable in relation to the heating element in the main direction of movement. However, the stirrer is preferably fastened to the holding device movably in the main direction of movement. Particularly preferred is an arrangement of the heating element and the stirrer in which the stirrer moves further into the container than the heating element. This makes it possible, for example, to use a stirring element which spreads open speed-dependently and, in the spread-open state, has a greater diameter than the outside diameter of the heating element.

The apparatus according to the invention may be provided with a sensor or a plurality of sensors, for example for sensing the temperature, the viscosity or the conductivity of the liquefied material or the torque of the stirrer shaft. Changes in the properties of the melt, such as the viscosity, can be concluded from a change in the speed of the stirrer or the torque thereof during operation.

A further subject matter of the invention is a method for melting a meltable material in a container that has an opening on its upper side, by means of the apparatus according to the invention, comprising the following steps:

-   -   placing the lower end of the heating element onto the surface of         the material to be melted through the opening in the container,     -   making the heat transfer medium flow through the heating         element,     -   lowering the heating element into the material as the         liquefaction of the material proceeds,     -   mixing already molten material through by rotation of the         stirrer.

Making the heat transfer medium flow through the heating medium does not necessarily have to be carried out as the second step, it may also be commenced already before the heating element is placed onto the surface of the material to be melted. The through-flow may take place continuously during the melting process or intermittently. The steps of lowering the heating element and performing mixing through by the rotation of the stirrer may be carried out successively or at the same time as one another. They may also be carried out alternately one after the other.

The heat transfer medium is chosen in dependence on the melting range of the material to be melted. For a wide application area, warm to hot water with flow temperatures of 60 to 90° C. are suitable. If the melting range of the material to be melted requires a higher flow temperature, superheated water or water-steam mixtures up to a temperature of about 160° C. under a pressure of 4 bar are suitable. For still higher temperatures, heating by steam alone is recommendable, in the last-mentioned cases the components of the heating element having to be of a pressure-resistant configuration. It goes without saying that, depending on availability and the specific application, other heat transfer media may also be used, for example oils such as Marlotherm oil. They should be used in particular whenever water is not appropriate for safety reasons, for example if the container content would react violently with water in the event of a leakage.

A further subject matter of the invention is a method for cooling a molten material in a container that has an opening on its upper side, by means of the apparatus according to the invention, comprising the following steps:

-   -   introducing the heating element into the molten material through         the opening in the container,     -   making a cold heat transfer medium flow through the heating         element,     -   after the material has solidified, raising the temperature of         the heat transfer medium briefly to melt the heating element         free,     -   withdrawing the heating element from the melted-free region.

Making the cold heat transfer medium flow through the heating medium does not necessarily have to be carried out as the second step, it may also be commenced already before the heating element is introduced into the molten material. The through-flow may take place continuously during the melting process or intermittently.

The cold heat transfer medium is chosen in dependence on the melting temperature of the material to be cooled. Suitable are, for example, cold water, cooling water, brine or some other substance if water cannot be considered for the safety reasons already referred to above.

By immersing the heating element in the molten material, the latter can be cooled quickly and efficiently and, depending on its melting point, possibly made to solidify. In the case of a solidified material, a warm or hot heat transfer medium may be briefly made to flow through the heating element, so that the material in its direct vicinity liquefies. Subsequently, the melted-free heating element is removed from the container and possibly left to drip. The method for cooling a molten material is advantageously used when an end product is to be rapidly cooled or solidified, for example in order to make it quickly ready for transportation or to prevent crystallization of the material.

Furthermore, it can also be used for rapidly cooling liquids from the food industry, which may occur in a warm state or else be heated briefly for the purpose of sterilization, for example wine, milk or fruit juices.

In an advantageous configuration of the method according to the invention, the flow temperature to the heating element is set to a predetermined temperature. Appropriate thermostats or temperature control devices are known to a person skilled in the art.

To protect against undesired reactions in the container, for example oxidations with atmospheric oxygen, a shielding gas may be introduced into the container while the method is being carried out. This gas is preferably nitrogen.

The method according to the invention is suitable in particular for melting and/or cooling

-   -   solid hydrocarbons or derivatives thereof, for example waxes and         paraffins,     -   polyether glycols, derived from polyethylene, polypropylene or         polybutylene glycols or mixtures thereof, which may also be in         an alkylated form,     -   fats or solid fat-water emulsions,     -   solid salts, ionic liquids, metals or alloys,     -   solid mono-, di- or polyisocyanates, low-molecular-weight         prepolymers or silicones,     -   solid sulfur or organic anhydrides such as maleic anhydride or         phthalic anhydride.

The methods according to the invention are suitable for various transporting containers, in particular for drums, shipping containers, railroad wagons, container trucks and road tankers. Depending on the specific application, a plurality of apparatuses according to the invention may also be used.

The invention makes it possible for the content of a transporting container to be gently melted and heated by the direct contact of a heated heating element with the material to be melted in the container. By creating a flow in a melt by stirring while the heat is being introduced into the melt, the container content is additionally mixed through homogeneously, and the duration of the melting process is reduced considerably in comparison with known methods. As a result, potentially harmful side-effects of the melting process, such as thermal damage to the material or undesired reactions in the container, are also significantly minimized. The apparatus according to the invention is of a simple structure and can be used flexibly.

The invention is further explained below on the basis of the drawings, which should be understood as basic representations. They do not represent any restriction of the invention, for example with regard to actual dimensions or configurational variants of components. For the sake of better representation, they are generally not to scale, in particular with regard to relative lengths and widths. In the drawings:

FIG. 1 shows an embodiment of an apparatus according to the invention with a double helix as a heating element

FIG. 2 shows a detail taken from FIG. 1

FIG. 3 shows an example of use of an apparatus according to the invention for the continuous melting of solid flakes

FIG. 4 shows an embodiment of an apparatus according to the invention for use in drums

LIST OF REFERENCE NUMERALS USED

-   -   10 . . . Heating element     -   11 . . . Inflow opening     -   12 . . . Outflow opening     -   13 . . . Inflow line     -   14 . . . Outflow line     -   15 . . . Tube helix     -   16 . . . Reinforcing element     -   20 . . . Holding device     -   21 . . . Guiding rod     -   22 . . . Guiding sleeve     -   23 . . . End stop     -   30 . . . Stirrer     -   31 . . . Stirrer shaft     -   32 . . . Stirring element     -   33 . . . Motor     -   40 . . . Container     -   41 . . . Insulated container wall     -   42 . . . Wire screen     -   43 . . . Filling hopper     -   44 . . . Outlet for melt     -   45 . . . Solid flakes     -   46 . . . Melt     -   47 . . . Gas inlet

In FIG. 1, a preferred embodiment of an apparatus according to the invention is represented. The heating element 10 is formed in a tubular manner as a double helix 15, which has a hollow-cylindrical contour. The two part-helixes have the same outside diameter of the hollow cylinder and run one into the other in the axial direction. The axial distance between neighboring tube portions is alternately 0% and 200% of the tube outside diameter, that is to say on one axial area the part-helixes are touching, while the other areas are at an axial distance that corresponds to twice the tube outside diameter. At their respective one end, in FIG. 1 the lower end, the part-helixes are connected to one another. With their respective other end, the part-helixes open out into the inflow opening 11 or into the outflow opening 12. The inflow opening 11 and the outflow opening 12 are located on the end face of the hollow cylinder that is facing away from the container during moving in and out. For a heat transfer medium to flow through, the two openings are connected to an inflow line 13 and an outflow line 14. To strengthen the hollow cylindrical structure with respect to radial bending, in the example represented three band-shaped reinforcing elements 16 are provided, running axially on the outer side of the double helix and fixedly connected, for example welded or brazed, to at least some tube portions.

The holding device 20 comprises two guiding rods 21, on which a guiding sleeve 22 is slidingly mounted. In order to prevent the guiding rods 21 from sliding out of the guiding sleeve 22, they are respectively provided at their lower ends with an end stop 23. The end stop 23 can preferably be set variably along the guiding rods 21, in order to be able to limit the depth of immersion of the heating element 10 in a container. The guiding sleeve 22 is connected to the inflow tube and the outflow tube of the double helix 15.

The holding device 20 may be fixed in place, for example on a wall, a top surface or a freestanding framework, or it may be used in a mobile manner, for example with its lower end mounted on a transporting container. In the case of an advantageous configuration with a fixed-in-place mounting, the holding device is fixedly connected to a wall. The transporting container to be handled is placed under the holding device. The heating element and the stirrer can be placed onto the material to be melted by being moved on the holding device in the main direction of movement vertically downward through the opening in the upper side of the transporting container. The heating element and the stirrer are preferably moved by means of a manually or electrically operated cable winch.

In the space inside the hollow-cylindrical double helix 15, a stirrer 30 is coaxially arranged. It comprises a stirrer shaft 31 and, in this example, three stirring elements 32 fastened thereto. FIG. 2 shows the lower end of the apparatus from FIG. 1 as a detail. The stirrer shaft 31 and the stirring elements 32 fastened thereto can be seen more clearly from this illustration. Not shown in the illustrations is the mounting of the stirrer shaft 31. It may take place independently of the mounting of the heating element, in order to allow an axial relative movement between heating element 10 and the stirrer 30. The axial relative movement makes it possible to move the stirrer further into the container than the heating element. This makes it possible, for example, to use a stirring element which spreads open speed-dependently and, in the spread-open state, has a greater diameter than the outside diameter of the heating element.

In order to liquefy the content of a transporting container, for example an IBC, the apparatus according to FIG. 1 is placed with its holding device 20 onto the opening in the upper side of the container. The heating element 10 is placed onto the solid content of the container and put into operation, by making warm or hot heat transfer medium, for example hot water, flow through it. The material in the direct vicinity of the tube helix 15 begins to melt, whereupon the heating element 10 is immersed in the melt on account of its dead weight or by being guided downward. The stirrer 30 inside the heating element 10 is likewise immersed in the melt being created. As soon as one or more of the stirring elements 32 is in the melt, the stirrer is switched on. The flow induced in the melt as a result has the effect that the heat transfer between the heat transfer medium and the material to be melted is improved significantly. Moreover, the melt is in this way homogenized. After some time, the container content is completely melted and homogeneously mixed. The stirrer 30 is switched off, the heating element 20 is removed from the container and left to drip. Then a desired amount of liquid, homogeneously mixed material can be removed from the transporting container.

Experience shows that only a small part of the energy introduced by the heat transfer medium is required for melting the solid material. It is therefore also possible to connect a plurality of apparatuses in series or parallel and operate them energy- and cost-efficiently. It is also advantageously possible to provide a control system which optimizes the melting process, by increasing the energy input whenever there is sufficient melt to take up the thermal energy. A preferred control strategy envisages, for example, initially melting the material with a low energy input, until the heating elements have been lowered to a predetermined length, and subsequently increasing the temperature of the heat transfer medium and/or the through-flow of heat transfer medium.

In a preferred configuration, three to five apparatuses according to the invention are interconnected on the heat transfer medium side, the heat transfer medium is pumped in a circulated manner and the energy required for input into the melt is introduced continuously into the circulation, for example by a heat exchanger or an inflow of heat transfer medium at a higher temperature than that in the circulating flow. Hot condensate from a processing plant can be advantageously used for this, for example.

Apart from the discontinuous use for liquefying solid container contents, the apparatus according to the invention can also be used continuously. FIG. 3 shows an example of the use of an apparatus according to the invention in a continuous process for melting solid flakes. Shown as a basic diagram is a longitudinal section through a container 40, which comprises an upper cylindrical part and a conical part adjoining said cylindrical part in the downward direction. The container wall 41 is preferably of a heat-insulated configuration. In the top of the container there is a filling hopper 43 for solid flakes 45, which is equipped with a closure flap for the metering of the flakes. At the lower end of the conical part there is an outlet 44 for the melt 46. Provided at the transition from the cylindrical part to the conical part is a wire screen 42, the mesh width of which is dimensioned in such a way that only the melt can flow into the conical part, and any flakes that there may still be in the melt are held back.

In a further opening in the top, the holding device 20 of an apparatus according to the invention is fastened. Its construction corresponds substantially to that represented in FIG. 1. Only the holding device 20 has been modified. The inflow tube and the outflow tube are each fastened to a guiding rod. The two guiding rods are slidingly mounted in two sleeves, which are connected fixed-in-place to the top of the container by means of the holding device 20. The length and position of the elements of the holding device have been chosen such that the lower end of the apparatus in the completely lowered state is just above the wire screen 42.

The method for continuously melting solid flakes may, for example, proceed as follows: firstly, flakes 45 are fed a little at a time into the interior of the container, until they have reached such a height from the wire screen 42 that they come into contact with the heating element 10. The heating element 10 is put into operation and hot water is made to flow through as a heat transfer medium. The melt 46 collects in the lower, conical part of the container, while flakes continue to be fed in continuously through the filling hopper 43. As soon as about half of the container is filled with melt, a continuous melt discharge through the outlet 44 is begun. While the flakes are being supplied, nitrogen is added as a shielding gas via a gas inlet 47.

This melting method can be advantageously used to supply a downstream plant continuously with a molten starting material, for example one of the substances mentioned above. For a polyethylene glycol (PEG 6000, melting range about 45° C. to 60° C.), for example, a heating element with a ratio of length to outside diameter of 1.5 is suitable if it is operated with hot water at about 80° C. For protection from an oxidation reaction, nitrogen is fed to the container at a volumetric flow of 80 liters per minute.

EXAMPLES

In Examples 1 to 4 described below, an embodiment of the apparatus according to the invention that corresponded in principle to the one represented in FIG. 1 was used. The heating element was produced from a high-grade steel tube with a wall thickness of 1.5 mm and an inside diameter of 9 mm. The heating element comprised a double helix with an outside diameter of the hollow cylinder of 13.5 cm and a length of the double helix of 72 cm. The axial distance between neighboring tube portions was 200% of the outside diameter of the tube. The stirrer was pneumatically driven and speed-controlled. Three propeller stirrers were arranged at a respective distance of 20 cm on the stirrer shaft as stirring elements. The outside diameters of the propeller stirrers were about 8 cm.

Example 1

An IBC was filled with 750 kg of n-octadecane (melting point 20° C.). The mass was in the container in the form of a block of homogeneous solid material. The IBC was open at the top, and the lower end of the holding device of the apparatus according to the invention was placed onto the rim of the opening. The heating element was movable in the vertical direction and was placed with its lower end onto the mass of solid material. To heat the solid material, hot water was made to flow through the heating element as a heat transfer medium. The water was gravimetrically fed into the heating element from a condensate tank at a flow temperature of about 80° C. and a volumetric flow of about 5 l/min. The water emerging from the outlet of the heating element was discarded. After approximately 60 minutes, the heating element had melted its way into the solid material over the complete length of the tube helix, whereupon the stirrer was switched on at a rotational speed of about 200 rpm. After a total of 12 hours, the entire content of the container was melted and homogeneously mixed through.

The heating element was withdrawn from the IBC and left to drip. After two minutes, it was sufficiently clean to be placed onto the next container. In the interim, a heatable feed pump and a trace-heated line were connected to the bottom tap of the IBC and the container was pumped empty for the material to be put to further use.

Comparative Example 1

An IBC comparable to Example 1 was introduced into a heating cabinet (the Conthermo company, heating area of 50 m², steam-heated at 4 bar) with a heated spatial volume of 2.3 m³ and a set ambient temperature of 70° C., and the top of the IBC was loosened sufficiently for pressure equalization. The melting process was visually checked every two hours to monitor its progress. Only after 63 hours in the heating cabinet was it found that the content had melted completely. The container was removed from the heating cabinet and its content processed further.

Example 2

The test arrangement corresponded to that in FIG. 1, with the difference that the IBC was filled with 750 kg of the wax mixture LINPAR® 18-20 (supplied by the Sasol company). The wax mixture consists mainly of n-alkanes of a chain length of C17 to C19 and has a melting point of about 30° C. After about 15 minutes, the tube helix had melted into the wax mixture over its entire length, whereupon the stirrer was switched on. After a total of six and a half hours, the total content of the container had melted, and a partial amount of 145 kg was removed.

Comparative Example 2

Under the same conditions as in Comparative example 1, a wax mixture LINPAR® 18-20 in an IBC was placed into a heating cabinet. After 33 hours, the mixture had melted completely, and the IBC was removed from the heating cabinet. With an inserted stirrer, the content of the IBC was homogenized for a time of 10 minutes, before a partial amount of 145 kg of the wax mixture could be removed.

Example 3

The test arrangement corresponded to that in Example 1, with the difference that the IBC was filled with 750 kg of a mixture of saturated n-paraffinic hydrocarbons (melting range about 27° C. to 31° C.). After about 30 minutes, the tube helix had melted into the mixture over its entire length, whereupon the stirrer was switched on. The entire melting process of the complete IBC content took 8 hours. After the melting, a partial amount could be removed from the IBC.

Comparative Example 3a

Under the same conditions as in Comparative example 1, a mixture according to Example 3 in an IBC was placed into a heating cabinet. After 37 hours, the mixture had melted completely, and the IBC was removed from the heating cabinet. With a stirrer placed on, the content of the IBC was homogenized for a time of 30 minutes, before a partial amount of the mixture could be removed.

Comparative Example 3b

A commercially available, electrically operated heating band was wound around an IBC according to Example 3 and used to heat it. After heating for a week, the content had still not melted and the test was abandoned.

Example 4

A clamping ring drum with a capacity of 200 liters was filled with 210 kg of a solid emulsifier (melting point about 26° C.). The main constituent of the emulsifier was p-octylphenol ethoxylate with about 25 mol EO. The mass was in the drum in the form of a block of homogeneous solid material. The lid of the drum was removed, and the lower end of the holding device of the apparatus according to the invention was placed onto the rim of the opening. All further method steps corresponded to those described in Example 1, water with a flow temperature of 67° C. being used as a heat transfer medium. The stirrer was switched on about one hour after the beginning of the melting process. After 14 hours, the entire content of the drum had melted, and, to dilute it, the melt could be pumped into a reaction vessel already containing hot water.

Comparative Example 4a

Under the same conditions as in Comparative example 1, a drum with emulsifier according to Example 4 was placed into a heating cabinet. After 67 hours, the content of the drum had melted completely.

Comparative Example 4b

Four pallets each with four sealed drums according to Example 4 were introduced and completely immersed in a tank with dimensions of 4×3×2 meters (length×width×depth), which was filled with 15 m³ of water. A constant stream of steam was introduced into the tank for two days, whereby the water heated up and the content of the drums was heated continuously. Experience shows that, after keeping them in the tank for two days, the content of the drums was melted through completely. This conventional method is complicated and very energy-intensive. Moreover, sampling or monitoring of the melting process is only possible if a complete pallet is extracted. It has also proven to be disadvantageous that treatment of this kind very soon makes the drums begin to rust.

Example 5

In the two examples described below, an embodiment of the apparatus according to the invention that corresponded in principle to the one represented in FIG. 4 was used. The heating element 10 was produced from a high-grade steel tube with a wall thickness of 1.5 mm and an inside diameter of 9 mm. The heating element comprised a single tube helix 15 with an outside diameter of the hollow cylinder of 40 cm and a length of the tube helix of 60 cm. The axial distance between neighboring tube portions was 100% of the outside diameter of the tube. The upper end of the tube helix 15 opened out into the inflow opening 11. The lower end of the tube helix 15 was guided upward as a straight piece of tube on the inner side of the hollow cylinder and opened out into the outflow opening 12. To strengthen the hollow cylindrical structure with respect to radial bending, four band-shaped reinforcing elements 16 were provided, running axially on the outer side of the double helix and fixedly connected to at least some tube portions.

The heating element was designed with a view to melting material in drums. The diameter of the hollow cylinder was chosen such that, when seen in cross section perpendicularly to the axis of the hollow cylinder, the area content of the circle within the hollow cylinder corresponds substantially to the area content of the circular ring between the hollow cylinder and the inner wall of the drum. The test results presented below were obtained with the heating element without using a stirrer. In comparison with conventional methods for melting the material in the drums, it was possible to achieve much shorter times just with the heating element alone. When a stirrer is used, further reduced times can be expected for the melting process as a result of the better mixing through.

Example 5a

The apparatus according to the invention was placed into an empty clamping ring drum with a capacity of 200 liters and the heating element as described in Example 1 was put into operation. 100 kg of maleic anhydride flakes (melting point 53° C.) were fed into the drum and melted while venting. The melting process for the entire amount of 100 kg took one hour.

Example 5b

The apparatus according to the invention was placed into an empty clamping ring drum with a capacity of 200 liters and 100 kg of polyethylene glykol 6000 (melting range about 45° C. to 60° C.) was introduced in the form of flakes. With hot water at a temperature of about 90° C. as a heat transfer medium, the heating element was then put into operation. After six hours, the complete content of the drum had melted, so that the melt could be pumped into a storage tank.

For the next melting process, 100 kg of flakes (four bags of 25 kg each) were again introduced into the clamping ring drum.

Comparative Example 5b

The clamping ring drum filled with flakes was placed in a heating chamber, the inside ambient temperature of which had been set to 90° C. After 19 hours, the content of the drum had melted completely and could be removed for further use.

Most of the tests described above were carried out in winter. The temperature of the material to be melted before the beginning of the melting process was not determined. However, it was the same in the examples and associated comparative examples, since the transporting containers and drums were kept outdoors or in unheated sheds at the same location.

Examples 6 and 7 illustrate the possibilities for using the apparatus according to the invention for cooling meltable material. They have not yet been confirmed experimentally.

Example 6

A catalyzed solvent-free conversion of a mixture of two different bifunctional isocyanates with a mixture of two diols and a triol is carried out at 110° C. in a reaction vessel with a reaction volume of 10 m³ to obtain a viscous polyurethane melt. The size of the batch is around six tonnes. After completion of the conversion, the reaction product has to be fed into seven prepared IBCs, while the cooling process is intended to be carried out quickly and under supervision, since the reaction product continues to react as the viscosity increases at the temperature concerned here. For being filled, the IBCs stand next to one another and each IBC is equipped with an apparatus according to the invention as described above, which are respectively introduced into the empty IBCs. The apparatuses are connected in series to a common cooling circuit and serve for cooling the reaction product. Each of the stirrers is equipped with a stirrer speed monitor. The heating elements are interconnected on the countercurrent principle, opposite to the filling sequence of the IBCs. This has the consequence that the IBC to be filled at any one time comes into contact with the coldest stream of coolant.

As the temperature of the reaction product in the reaction vessel decreases, the viscosity of the mixture increases greatly. It is therefore not expedient to cool the reaction product in the reaction vessel completely. After complete conversion, the mixture is merely cooled to an internal temperature of about 75° C. and introduced by means of heated lines from the reaction vessel into the IBCs via their bottom tap by further pressurization by means of nitrogen. Once the filling of one IBC has been completed, the lines are blown free by means of a surge of nitrogen and the bottom tap concerned is closed.

On the apparatuses, the stirrer shaft has been lowered approximately 10 cm with respect to the lower end of the tube helix and is immersed in the product before the helix. When the surface of the melt rises and comes into contact with the tube helix, slow cooling commences, but only has an effect when the container is completely filled and no further hot product flows in. The temperature of the product is lowered while at the same time its own viscosity increases, until the increasing viscosity leads to a reduction in the stirrer speed. If the speed drops below a predetermined, product-dependent value, the respective apparatus is withdrawn from the melt of the IBC. After a cooling time of approximately 3 h, the temperature inside the IBCs has fallen to approximately 45° C. Once all the IBCs have been filled and the apparatuses have been withdrawn from the IBCs, the cooling is stopped and hot water is passed through the tube helix in order to liquefy any remains of product that are attached and make them drop into the IBCs. After that, the IBCs are closed for transportation.

Example 7

To prepare a defined wax mixture comprising 2 parts n-octadecane, 1 part n-eicosane (C₂₀H₄₂, melting range 36-39° C.) and 1 part n-docosane (C₂₂H₄₆, melting range 41-44° C.), the contents of four separate IBCs with the raw materials analogous to Example 1 are melted and successively pumped into a dry stirred reaction vessel that has been filled with nitrogen and preheated to 60° C. and are homogenized for a time of 30 minutes. The apparatuses according to the invention are switched over to cooling and brine heated to +10° C. is made to flow through them. The liquid wax mixture is forced back out of the stirring vessel into the IBCs, whereby the IBCs are filled. When the liquid wax melt comes into contact with the cool tube helixes, the mass solidifies quickly and grows outward around the tube helix. The cooling is maintained until the entire content of the IBCs is completely solidified and in the form of a block, which is the case after about 6 hours. The temperature of the heat transfer medium is then increased to 43° C. for a time of three minutes, in order that the material surrounding the tube helix can liquefy and the apparatuses can be withdrawn from the IBCs. In comparison with the conventional method, in which the container content is not actively cooled but solidifies slowly, a more homogeneous distribution of the container content is achieved by the method according to the invention. To verify this, drilled samples can be taken at various points in the IBC and analyzed for their physical properties, such as the melting temperature. 

1. An apparatus for heating or cooling a meltable material in a container, comprising a heating element (10) and a holding device (20), the heating element (10) being of a tubular design, with an inflow opening (11) and an outflow opening (12) for a heat transfer medium to flow through, and being fastened to the holding device (20) movably in at least one spatial direction as the main direction of movement, wherein the apparatus also has a stirrer (30) for mixing liquid material through, which is likewise arranged movably in the main direction of movement.
 2. The apparatus according to claim 1, wherein the holding device (20) is designed in such a way that the heating element (10) and the stirrer (30) are movable in the vertical direction as the main direction of movement through an opening in the upper side of the container.
 3. The apparatus according to claim 1, the heating element (10) comprising a tube helix (15), which has a hollow-cylindrical contour, and the axis of the cylinder corresponding substantially to the main direction of movement.
 4. The apparatus according to claim 3, the axial distance between neighboring tube portions being from 20% to 400%, preferably from 50% to 200%, on the outside diameter of the tube.
 5. The apparatus according to claim 3, the tube helix (15) comprising two part-helixes with the same outside diameter of the hollow cylinders, the part-helixes running one into the other in the axial direction, being connected to one another at their respective one end and opening out into the inflow opening (11) or the outflow opening (12) with their respective other end.
 6. The apparatus according to claim 3, the tube helix (15) comprising two part-helixes with different outside diameters of the hollow cylinders, the part-helixes running one into the other in the radial direction, being connected to one another at their respective one end and opening out into the inflow opening (11) or the outflow opening (12) with their respective other end.
 7. The apparatus according to claim 3, the heating element (10) being dimensioned in such a way that the ratio of its length to its outside diameter is from 1 to 10, preferably from 1.5 to 8, in particular from 2 to 6, and the outside diameter of the heating element (10) being from 4 to 60 cm, preferably from 8 to 20 cm, in particular from 10 to 16 cm.
 8. The apparatus according to claim 3, the stirrer (30) comprising a stirrer shaft (31), on which at least one stirring element (32) is arranged, and the axis of which corresponds substantially to the main direction of movement.
 9. The apparatus according to claim 8, the stirrer shaft (31) being arranged inside the hollow-cylindrical tube helix (15).
 10. The apparatus according to claim 1, the heating element (10) and the stirrer (30) being fastened on the holding device (20) movably in the main direction of movement independently of one another.
 11. A method for melting a meltable material in a container that has an opening on its upper side, by means of an apparatus according to claim 1, which comprises the steps of: placing the lower end of the heating element (10) onto the surface of the material to be melted through the opening in the container, making the heat transfer medium flow through the heating element (10), lowering the heating element (10) into the material as the liquefaction of the material proceeds, mixing already molten material through by rotation of the stirrer (30).
 12. A method for cooling a molten material in a container that has an opening on its upper side, by means of an apparatus according to claim 1, which comprises the steps of: introducing the heating element (10) into the molten material through the opening in the container, making a cold heat transfer medium flow through the heating element (10), after the material has solidified, raising the temperature of the heat transfer medium briefly to melt the heating element (10) free, withdrawing the heating element (10) from the melted-free region.
 13. The method according to claim 11, the container being a drum, a transporting container, a railroad wagon, a container truck or a road tanker. 